Methods of forming metal-comprising materials and capacitor electrodes; and capacitor constructions

ABSTRACT

The invention includes a method of forming a metal-comprising mass for a semiconductor construction. A semiconductor substrate is provided, and a metallo-organic precursor is provided proximate the substrate. The precursor is exposed to a reducing atmosphere to release metal from the precursor, and subsequently the released metal is deposited over the semiconductor substrate. The invention also includes capacitor constructions, and methods of forming capacitor constructions.

TECHNICAL FIELD

The invention pertains to methods of forming metal-comprising materials,such as, for example, capacitor electrodes. The invention also pertainsto capacitor constructions.

BACKGROUND OF THE INVENTION

Capacitor constructions are utilized in numerous semiconductorstructures, such as, for example, memory arrays. An exemplary memoryarray is a dynamic random access memory (DRAM) array, with individualDRAM cells of the array comprising a capacitor and a transistor.

Capacitor constructions comprise a first conductive capacitor electrodeand a second conductive capacitor electrode, separated by a dielectricmaterial. Among the compositions suitable for utilization as capacitorelectrodes are metals, such as, for example, platinum, rhodium, iridium,ruthenium, etc. The metals can be deposited by exposing ametallo-organic precursor material to an oxidizing ambient (such as, forexample, an ambient O₂, O₃, and/or N₂O) to break down the precursor andrelease the metal. The released metal can then deposit on a substrate toform a metal film which is ultimately incorporated into a capacitordevice as a capacitor electrode.

A difficulty which can occur during oxidation of the metallo-organicprecursors is that materials associated with a semiconductor substrateare exposed to the oxidizing conditions, and can themselves becomeoxidized or otherwise degraded during the degradation of themetallo-organic precursors. Accordingly, it would be desirable todevelop alternative methods for formation of metallic materials onsemiconductor substrates, other than the oxidation of metallo-organicprecursors.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a method of forming ametal-comprising mass for a semiconductor construction. A semiconductorsubstrate is provided, and a metallo-organic precursor is providedproximate the substrate. The precursor is exposed to a reducingatmosphere to release metal from the precursor, and subsequently thereleased metal is deposited over the semiconductor substrate.

In another aspect, the invention encompasses an embodiment of forming ametal-comprising mass for a semiconductor construction wherein ametal-comprising precursor is exposed to ammonia to release metal fromthe precursor, and subsequently the release metal is deposited over asemiconductor substrate.

In another aspect, the invention encompasses methodology for formingcapacitor electrodes wherein a metal-comprising precursor is exposed toa reducing ambient to deposit a metal-comprising mass which ultimatelyis incorporated into a capacitor construction as a capacitor electrode.

The invention also includes capacitor constructions.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawing.

The FIGURE is a diagrammatic, cross-sectional view of a semiconductorwafer fragment illustrating an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention is described with reference to asemiconductor wafer fragment 10 in the FIGURE. Fragment 10 includes asubstrate 12, which can comprise, for example, monocrystalline silicon.To aid in interpretation of the claims that follow, the terms“semiconductive substrate” and “semiconductor substrate” are defined tomean any construction comprising semiconductive material, including, butnot limited to, bulk semiconductive materials such as a semiconductivewafer (either alone or in assemblies comprising other materialsthereon), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductive substrates described above.

An insulative material 14 is formed over substrate 12, and can comprise,for example, borophosphosilicate glass (BPSG) and/or silicon dioxide. Anopening extends through insulative material 14 and to substrate 12, anda diffusion region 16 is formed within substrate 12 at a base of suchopening. Diffusion region 16 can be either n-type conductivity doped orp-type conductivity doped. Diffusion region 16 can be considered as anexemplary embodiment of an electrical node supported by substrate 12.

A series of conductive materials are formed within the opening in mass14, and extending above diffusion region 16. Such conductive materialsinclude a mass 18 of conductively-doped silicon, such as, for example,n-type or p-type doped polycrystalline silicon. The conductive materialsalso include a layer 20 of metal silicide, and a layer 22 comprisingmetal or metal nitride. It is noted that other conductive materials canbe used either alternatively, or in addition to the materials 18, 20 and22 illustrated in the FIGURE. For instance, material 18 can be replacedby a conductive metal plug, such as, for example, a titanium plug or atungsten plug. In other embodiments, a layer of metal-silicide can beprovided between diffusion region 16 and silicon-containing layer 18,with exemplary metal silicides comprising titanium silicide or tungstensilicide. Layers 18, 20 and 22 can be formed by conventional methods.

In particular embodiments, layer 22 can comprise, consist of, or consistessentially of, one or more of titanium nitride, tungsten nitride,tantalum nitride, elemental titanium, elemental tantalum or elementaltungsten; and layer 20 can comprise, consist of, or consist essentiallyof, titanium silicide or tungsten silicide. Layers 20 and 22 function asdiffusion and/or oxidation barriers.

A metal-containing mass 24 is formed over conductive layer 22, and inthe shown embodiment is in physical contact with layer 22. In accordancewith methodology of the present invention, mass 24 is formed by exposinga metallo-organic precursor to a reducing atmosphere to release metalfrom the precursor, and subsequently the released metal is deposited toform mass 24. In the shown embodiment, mass 24 is patterned into arectangular block. Such can be accomplished by, for example,photolithographic processing and an appropriate etch after deposition ofthe released metal. Appropriate photolithographic processing and etchingconditions will be recognized by persons of ordinary skill in the art.

Mass 24 can comprise, consist essentially of, or consist of one or moreof ruthenium, rhodium, iridium, cobalt, palladium, nickel or platinum.In a particular embodiment, mass 24 will consist of, or consistessentially of, ruthenium, and will be formed by exposingtricarbonyl-cyclohexadiene ruthenium precursor to a reducing ambientcomprising one or more of ammonia (NH₃), diatomic hydrogen (H₂), orplasma-activated hydrogen species. The reducing atmosphere can, inparticular embodiments, consist of, or consist essentially of, one ormore of ammonia, diatomic hydrogen or plasma-activated hydrogen species.In an exemplary embodiment, tricarbonyl-cyclohexadiene rutheniumprecursor is exposed to ammonia at a temperature of 210° C., and apressure of 4 torr for a duration of 120 seconds, to deposit mass 24 toa thickness of about 450 Å.

Prior art methodologies have existed wherein a metal-containing mass isformed over a layer identical to the above-described layer 22 byexposing a metallo-organic material to oxidizing conditions. However, aproblem with such prior art processes is that the oxidizing conditionscan oxidize various components of layer 22 to reduce the conductivity ofsuch layer. For instance, if layer 22 comprises titanium, tantalum ortungsten, the exposure of such layer to oxidizing conditions can formoxides of titanium, tungsten or tantalum. Such oxides are electricallyinsulative, and accordingly the desired conductive characteristics oflayer 22 are compromised, or in some cases even entirely lost, which canrender devices subsequently formed from layer 22 to be inoperable. Incontrast, the utilization of reducing conditions in embodiments of thepresent invention can avoid oxidation of the materials of layer 22, andaccordingly maintain the desired conductive characteristics of layer 22during formation of mass 24. A further advantage of utilizing reducingconditions in methodology of the present invention is that manymetallo-organic precursor materials contain oxygen, which can bereleased during chemical degradation of the precursor materials. Thereleased oxygen can oxidize substrate materials. However, utilization ofa reducing atmosphere can essentially scavenge the oxygen before itdeleteriously reacts with a substrate material. For instance, inparticular embodiments of the present invention, NH₃ can be utilized toessentially scavenge oxygen.

A reason that reducing conditions have not previously been utilized forforming conductive masses in semiconductor constructions is that thereis a concern that carbon from a metallo-organic precursor will depositwithin a conductive metal mass formed from the precursor unless theprecursor is exposed to oxidizing conditions. In one aspect of thepresent invention, it is recognized that carbon incorporation is lessproblematic in particular semiconductor fabrication applications than isoxidation of materials associated with a semiconductor device. Forinstance, in the embodiment described with reference to the FIGURE, itcan be highly desirable to maintain the conductive characteristics oflayer 22, and of less concern is elimination of carbon from mass 24.Accordingly, utilization of reducing conditions to form mass 24 ispreferred relative to utilization of oxidizing conditions, even if suchcauses an increase in carbon incorporation within mass 24 relative tothat which would occur with utilization of oxidizing conditions.However, an analysis of a mass 24 formed by exposingtricarbonyl-cyclohexadiene ruthenium precursor to ammonia has shown thatthere is very little carbon incorporation within such mass. Accordingly,in particular embodiments of the present invention, oxidation of layer22 can be avoided, and also carbon incorporation within mass 24 can beavoided. Such can be preferred embodiments of the present invention, butit is to be understood that the invention can also encompass embodimentswherein carbon incorporation occurs within mass 24.

Mass 24 can, particular embodiments, comprises multiple metals formedfrom one or more precursors. The multiple metals can include one or moreof ruthenium, rhodium, iridium, cobalt, palladium, nickel or platinum.In some aspects of the invention, it can be desired that mass 24 doesnot consist solely of platinum. However, in such aspects, mass 24 cancomprise platinum in combination with other metals. Accordingly, it canbe desired that mass 24 be formed from at least one precursor thatcomprises a metal other than platinum; but such at least one precursorcan be utilized in combination with other precursors that do compriseplatinum.

After formation of mass 24, a dielectric material 26 is provided overthe mass. Dielectric material 26 can comprise silicon dioxide and/orsilicon nitride. Additionally, or alternatively, dielectric material 26can comprise a so-called high-k material, such as, for example, Ta₂O₅.

After formation of dielectric material 26, a second capacitor electrode28 is formed over dielectric material 26. Capacitor electrode 28 cancomprise metal and/or conductively-doped silicon. If electrode 28comprises metal, such can be formed utilizing a reducing atmosphere aswas described previously for formation of mass 24. Alternatively,electrode 28 can be formed by exposing a metallo-organic precursor to anoxidizing atmosphere. In preferred embodiments of the invention,dielectric material 26 can comprise a high-k material, and electrode 28is formed by exposing a metallo-organic precursor to oxidizingconditions. The oxidizing conditions can cure oxide deficiencies thatcan otherwise exist in a high-k material. For instance, if the high-kmaterial comprises Ta₂O₅, there can be regions in the material whichhave an excess of tantalum relative to the amount of oxygen so that thematerial is tantalum-rich (i.e., so that there is more tantalum thanshould be present in the stoichiometric relationship Ta₂O₅). Suchtantalum-rich regions will lack the desired dielectric characteristicsof the high-k material. Exposure of the tantalum-rich regions tooxidizing conditions can convert such regions to Ta₂O₅, and accordinglyimprove the dielectric properties associated with the regions.

Second capacitor electrode 28 can comprise, consist of, or consistessentially of ruthenium, rhodium, iridium, cobalt, palladium, nickel orplatinum; and can comprise an identical metal to that utilized in mass24, or a different metal than that utilized in mass 24. In particularpreferred embodiments, mass 24 will be formed by exposing ametallo-organic precursor to a reducing environment, and will constitutea first capacitor electrode; and mass 28 will be formed by exposing thesame metallo-organic precursor, or a different metallo-organicprecursor, to an oxidizing atmosphere, and will constitute a secondcapacitor electrode.

The masses 24, 26 and 28 of the FIGURE together define at least aportion of a capacitor construction. Such capacitor construction can beincorporated into various semiconductor devices, such as, for example, aDRAM cell. In embodiments in which the capacitor construction isincorporated into a DRAM cell, there will typically be a transistor gate(not shown) utilizing diffusion region 16 as a source/drain region, andaccordingly electrically connected to mass 24 though diffusion region16. In such embodiments, mass 24 can be considered a storage node of acapacitor construction.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1-41. (cancelled). 42: A method of forming a conductive material,comprising: providing a semiconductor substrate; exposing one or moremetallo-organic precursors to a reducing atmosphere to release metalfrom at least one of said precursors, wherein said one or moreprecursors comprise carbon and one or more of Co, Pd, and Ni; anddepositing the released metal over the semiconductor substrate to form aconductive material on the semiconductor substrate. 43: The method ofclaim 42 wherein the substrate comprises an oxidizable upper surface.44: The method of claim 42 wherein the substrate comprises an oxidizableupper surface and wherein the conductive material is formed physicallyagainst the upper surface. 45: The method of claim 42 wherein thereducing atmosphere comprises H₂. 46: The method of claim 42 wherein thesemiconductor substrate comprises a conductive layer. 47: The method ofclaim 46 wherein the conductive layer comprises one or more of titaniumnitride, tungsten nitride, tantalum nitride, elemental titanium,elemental tantalum, and elemental tungsten. 48: The method of claim 47wherein the released metal is deposited directly on the conductivelayer. 49: The method of claim 42 wherein the semiconductor substratecomprises both a first layer comprising a metal suicide and a secondlayer comprising a metal nitride, the released metal being depositieddirectly on the second layer.